How Accurate Are DUI Tests?


Law enforcement officers utilize a variety of tests to determine whether a driver is too impaired to operate a car. Sometimes they will start with a field sobriety test, which tests a driver’s balance, coordination and cognitive skills. Walking in a straight line, balancing on one leg and following a flashlight with one’s eyes (called a horizontal gaze nystagmus test) are all common components of a field sobriety test. If a driver fails these tests, the officer might pursue a more accurate means of proving inebriation. But how accurate are the common drunk driving tests?

Blood vs. Breath Testing

Blood tests are the most accurate tests used to identify drunk drivers. In most cases, blood tests will show exactly how impaired a driver is, but it is possible for certain parts of the tests to be performed incorrectly. In rare cases, an improperly preserved sample could coagulate and decompose, making accurate readings impossible. The blood test could also be mixed up with or contaminated by other samples if proper protocol is not followed.

Breath tests do not measure the amount of alcohol in the blood, so the results of a breathalyzer test are less accurate than blood tests, but breathalyzers are much more accessible and can be performed on the spot at the scene of a drunk driving investigation. The science behind breathalyzers uses averages to determine BAC, and because of this, the results are different based on the person, body temperature and respiration rate. Breathalyzers can also give false positives; for example, using a breathalyzer on someone who has just used mouthwash will inflate the results.

Bear in mind that it is within your rights to refuse blood or breath tests, but by doing so you will violate Colorado’s implied consent laws and have your license revoked. If you are arrested for drunk driving, speak to a DUI attorney about your options going forward.

Thomas Law Firm – Denver Drunk Driving Lawyers

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